Here gitlab runs on a separate Qemu/KVM instance on a ~small Hetzner server. Performance is no topic.

(Though can't tell about the last two versions - we skip versions if not impressed and/or when we wait until something is finished (like e.g. the new ui now). We never update to x.x.0 as there is always an improved x.x.3 or so version worth waiting to).

it has. I never seen that any application (not even java) would take 2gb of memory (well site loading time and memory usage got better the last two releases, so it was worse) for a really really small instance. 3 users, 25 projects (only three are regulary updated). some sites do load really really slow (we only assigned two real numa cores to it). but projects load in like 1 second (which I think is really bad, when we browse it in our local lan 1gbit..) we were on jira, stash/bitbucket server before and they did take the same amount of memory (well you could trim it to use less). Well bitbucket server did not have the features and updating jira/stash was way worse than gitlab. (need to copy server.xml), but the performance was way way better, even on worse hardware. problem was jira > gitlab issues, gitlab > stash, however we only used 1% of all jira features, so we gave gitlab a try and we started to use it before they got crazy with their features.

The critical thing is to give it enough memory.

For a really small team with 6 developers and maybe 3 CI builds per hour, I had to give the Docker container 7GB ram to run well. (not including the CI runner)

It's ridiculous that it would need that much for a small setup, but any less and page load times get very slow.